Latent Curing Agent

Abstract

An aluminum chelate-based latent curing agent capable of curing a thermosetting epoxy resin under the condition of relatively low temperature in a short period of time is provided. Furthermore, a method for manufacturing the latent curing agent is provided, in which the curing conditions of the aluminum chelate-based latent curing agent can be controlled relatively easily.The aluminum chelate-based latent curing agent is prepared by reacting an aluminum chelate agent with a silsesquioxane type oxetane derivative in the presence of a water insoluble or poorly water-soluble cellulose ether, whereby latency properties are imparted thereto. This latent curing agent contains a coating layer composed of the water insoluble or poorly water-soluble cellulose ether. Preferably, the surface is treated with an isocyanate compound.

Description

TECHNICAL FIELD[0001]The present invention relates to an aluminum chelate-based latent curing agent capable of initiating curing of a thermosetting type composition at relatively low temperatures, a manufacturing method of the same, and a thermosetting type composition containing the same and having good storage stability.BACKGROUND ART[0002]Thermosetting type resin compositions such as epoxy resins have been widely employed as adhesive materials, molding materials, and the like. An imidazole-based latent curing agent has been employed as one of curing agents for such compositions. Such an imidazole-based latent curing agent does not exhibit curing ability under normal storage conditions and thus has been widely employed in order for a thermosetting epoxy resin composition to be used as a one-component type curable composition having good handleability and good storage stability. As a representative example of such an imidazole latent curing agent, a microcapsule-type imidazole late...

AI Technical Summary

Benefits of technology

[0014]The latent curing agent of the present invention is a latent curing agent to which latency properties are imparted by reacting an aluminum chelate agent with a silsesquioxane type oxetane derivative in the presence of a water insoluble or poorly water-soluble cellulose ether. The latency properties are considered to be achieved by the reason described below. That is, an oxetane ring in a silsesquioxane type oxetane derivative has higher nucleophilicity of ether oxygen than an oxirane ring and has excellent cationic polymerizability, and thus the silsesquioxane type oxetane derivative is polymerized through ring-opening by the action of the aluminum chelate agent. Furthermore, a silanol group may be formed when a part of alkoxysilyl groups in the polymer are subjected to hydrolysis by a very small amount of water in the polymerization system, or a silanol group may be present in the silsesquioxane type oxetane derivative from the outset. These silanol groups interact with the aluminum chelate agent, and therefore the aluminum chelate agent is combined and integrated with the polymerized material. Subsequently, the polymerization reaction is terminated, and the temperature of the solution of the polymerized material is lowered. Then, ethyl cellulose can no longer remain dissolved in the solution and forms a microcapsule wall around the polymerized material. Hence, latency properties are imparted to the nonaqueous type aluminum chelate-based curing agent. Therefore, the aluminum chelate agent, which is liquid at room temperatures, can also be employed as a latent curing agent.

[0015]Such a nonaqueous type aluminum chelate-based latent curing agent is capable of curing a thermosetting type compound such as an epoxy resin or an oxetane compound under the condition of relatively low temperature in a short period of time by melting the microcapsule wall. Furthermore, since this aluminum chelate-based latent curing agent can be manufactured in a nonaqueous solvent, the curing agent can be prevented from being inactivated, and the reduction of the curing performance can be suppressed.

Problems solved by technology

Therefore, a problem exists in that stable curing characteristics are not obtained since irregularity and unevenness are likely to be formed on the surface, and thus curing conditions are difficult to control.

Furthermore, the polymerization initiation temperature of a thermosetting epoxy resin composition into which such a curing agent is mixed is too low relative to an exothermic peak in DSC (differential scanning calorimetry).

Therefore, it is hard to say that latency properties are sufficient.

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